Process for the production of a crimped continuous multifilament yarn

ABSTRACT

Process and apparatus for producing a crimped continuous multifilament yarn by the sequential steps of air-jet texturizing to form multiple random filamentary loops, immediately pulling out metastable loops formed in the yarn without heating and without stretching or deforming the yarn filaments, next shrinking and heat setting the yarn at a temperature of about 150°-245° C., and then winding the yarn onto a spool at a predetermined yarn tension. The resulting spooled texturized yarn has valuable properties and characteristics in subsequent processing and textile operations.

BACKGROUND OF THE INVENTION

The invention relates to a method and apparatus for producing crimpedyarns composed of continuous synthetic fiber-forming polymericfilaments, especially polyethylene terephthalate filaments, wherein theyarn is guided between a first and a second set of feed and draw rollsor similar independently driven delivery systems, so that the yarnpasses with overfeed through a texturing nozzle operating according tothe air-jet or air-bulking principle to produce a large number of randomloops or crimps in the individual filaments. Other than the selection ofparticular filaments, the type and degree of texturizing or bulkingdepends largely upon the amount of twist in the initial yarn and theamount of overfeed through the texturizing jet. The resulting texturizedyarn is then directly spooled, usually under a high uniform tension. Theresulting yarn product is characterized by a poor linear stabiity andvery high boiling shrinkage values.

A general description of the air-jet texturizing process can be found insuch texts as "Woven Stretch and Textured Fabrics", by B. L. Hathorne,Interscience Publishers, John Wiley & Sons, N.Y., Chapter 6, pages104-117 (1964). More particularly, attention is directed to the Breenpatents and especially U.S. Pat. Nos. 2,783,609 and 2,852,906 which aredirected to the yarn product as well as the process and apparatus. Theyarns produced in this way are especially characterized by the presenceof many ring-like or crunodal loops irregularly spaced along the yarnsurface although there is usually a substantial number of loops orcrimps formed internally of the yarn as well.

A variation of this air-jet texturizing process has been disclosed byField in U.S. Pat. No. 2,962,794 for the purpose of producing a jettexturized yarn which is highly bulky and which exhibits an extremelyhigh extensibility under very slight tension, e.g. an extensibility ofat least one fifth again and preferably one half again the unextendedlength of the yarn with recovery to at most the arithmetic mean of theextended and unextended lengths. This process and the resulting yarnproduct differ from the earlier Breen process and its product in that arelatively low twist yarn is subjected to relatively high overfeed inorder to produce by the jet texturization a large number of so-called"meta-stable loops" which remain in the yarn at about zero tension butwhich are removed under a light to moderate tension. Field teaches aheat setting of these meta-stable loops into the yarn such that the endproduct is highly extensible due to the large extension and contractionof the preset loops.

From the Breen process and other previously known processes of thiskind, i.e. for the air-jet texturizing of a continuous multifilamentyarn, it has become evident that the texturized or bulked yarn producthas only a slight or insubstantial stability. In order to measure theamount of stability of the yarn, it is usually determined by using asample which has an initial length of one meter under a base load ofabout 1/100 grams per denier, subjecting this sample to a load of 1/3grams per denier for 30 seconds and then, after relieving the texturizedyarn again to the base load of 1/100 grams per denier for a period of 30seconds, measuring the length of the yarn. The "instability" can be readimmediately from a centimeter measuring stick as a percentage of theoriginal length of the texturized yarn. Thus, the instability ismeasured as the percentage increase in the standard yarn length of onemeter after a specified load applied for a specified time has beenremoved and the yarn permitted to return to its base load for a similarspecified period of time.

Up to the present time, it has not been possible to achieveinstabilities of less than 1% with such air-jet texturized yarns.Moreover, it has not been possible with such yarns to achieve smallershrinkage values in connection with boiling. Hitherto, boiling shrinkagevalues have been more than 4%. Also, it has been previously necessary torespool the texturized yarn once again, first because the yarn spoolproduced directly in the texturizing operation exhibits such poorrun-off properties that it is impossible to introduce these spoolsdirectly onto a knitting or weaving machine. In particular, frequentthread breakage is caused and represents a serious problem in using eventightly wound initial spools which have not been rewound. Likewise,respooling has been deemed necessary in order to produce low-shrinkagedyeing spools which, as is known, may only have slight thread or yarntensions. Also, flat webs or sheets as finished articles produced fromthe known jet-texturized or air-bulked yarns are not onlydisadvantageous with respect to their inherent instability and theirlarge boiling shrinkage, but are also disadvantageous due to a verynoticeable "burr effect" which becomes apparent from the fact that thesurfaces of the flat articles adhere to each other.

Another disadvantage of yarns produced according to the conventionalair-jet texturing method is the nonuniformity of the crimping or loopingeffect. Previously, this lack of uniformity could only be partly reducedby providing the longest possible free running length of the yarn justbefore the final winding or spooling step.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide a process for thejet-texturizing of a synthetic multifilament yarn and especially apolyester yarn which will avoid the disadvantages of the prior artprocesses while permitting the yarn to be conducted through a number ofsequential treatment stages which can be made relatively independent ofone another in such a way that, in each stage of the process, therequired parameters or treatment conditions can be optimally selectedwithout making a compromise as between the functions of each individualstage, i.e. so that one stage does not have an undesirable influence onthe other stages.

It has now been found that highly improved results can be achieved inthe generally known air-bulking or jet-texturizing of a multifilamentyarn provided that the following independent steps or stages are carriedout in sequence:

(a) conducting the initial non-crimped multifilament yarn through anair-jet texturizing nozzle at an overfeed rate which is sufficient toform multiple random loops in the individual filaments including a minorproportion of metastable loops;

(b) conducting the yarn immediately after it has left the texturizingzone or stage between two delivery systems, e.g. feed and draw rolls,with a run-out speed greater than the run-in speed such that metastableloops are pulled out of the yarn under heat-free conditions such thatmetastable loops are pulled out of the yarn without causing any elasticor plastic deformation of the individual filaments, thereby providing astabilizing stage or zone in which a predominant number up to almost allof the metastable loops are eliminated or at least pulled out to astable position;

(c) then conducting the stabilized yarn by means of yet another deliverysystem which has a run-out speed which allows a shrinkage of the yarn bya predetermined amount with the yarn passing through a setting zonewhere it is subjected to a shrinking treatment and heat treatment attemperatures of from 150° C. up to about 245° C.; and

(d) thereafter winding the yarn onto a spool at a predetermined yarntension and at a winding speed less than the speed of the yarn into theair-jet texturizing nozzle.

The process of the invention is thus characterized by four distinctoperating stages or zones, namely; (1) a texturizing zone provided by anair-jet texturizing nozzle arranged between a first and second yarndelivery system operating at an overfeed rate corresponding to acircumferential speed V₂ of the second delivery system which is lessthan the circumferential speed V₁ of the first delivery system; (2) aheat-free stabilizing zone in which the yarn preferably runs free to aseparate third delivery system over an unheated interval from saidsecond delivery system with the run-out speed V₃ of the third deliverysystem being greater than the run-in speed V₂ so that the unstable orso-called metastable loops are carefully pulled out of the yarn undercontrolled conditions which prevent elastic or plastic filamentarydistortion; (3) a setting zone through which the yarn is conducted bymeans of a separate fourth delivery system having a run-outcircumferential speed V₄ which allows for a shrinkage of the yarn, theyarn in this setting zone being conducted under applied heat attemperatures of about 150°- 245° C. to cause both shrinkage and aheat-setting of the stabilized yarn; and then (4) a take-up stage orzone after said shrinkage where the yarn is wound onto a take-up spool,bobbin or the like at a winding speed V₅ which is less than V₁.Especially preferred features of the process are disclosed more fullyhereinafter and in the accompanying claims. The yarn product obtained bythis process is especially characterized by a boiling shrinkage of lessthan 3.3% and an instability of less than 1.0%, measured in the mannermentioned above.

The process of the invention is especially useful with a multifilamentyarn of a polyethylene terephthalate which has been spun at a spinningspeed of more than 2,500 meters per minute and subsequently stretched ina feed to draw ratio of 1:1.2 to 1:2 before being introduced into theair-jet texturizing zone, thereby providing a continuous spinning,stretching and air-jet texturizing at relatively high speeds directlyinto a spooled product that is ready for use in all subsequent textileoperations required of a produced spool package.

Apparatus for the invention closely follows the above named fouressential zones or stages of the process so as to essentially include: afirst and second yarn delivery means having an air-jet texturizingnozzle arranged therebetween; a third yarn delivery means to receiveyarn from the second yarn delivery means at a spaced interval sufficientto provide a heat-free stabilizing zone and preferably including controlmeans to variably operate said third delivery means at a run-out speedfrom the stabilizing zone of about 2 to 30% and most preferably about 2to 15% greater than the run-in speed to said stabilizing zone; a heatingmeans for shrinkage and setting of the yarn following the third yarndelivery means; and winding means to collect and preferably spool theresulting texturized yarn product at a controlled yarn tension. Aconventional draw means is advantageously arranged directly before thefirst yarn delivery means in order to stretch melt-spun syntheticfiber-forming continuous filaments. The stretching of freshly melt-spunfilaments can thus be accomplished by providing as the draw means thefirst yarn delivery means coupled with a yarn feed means operable at arun-in speed lower than the run-out speed of said first yarn deliverymeans. The specific types of apparatus useful in the present inventionare essentially dictated by the process stages or zones which follow oneanother in sequence so that one skilled in this art can readily selectthe needed apparatus once the process is defined.

DETAILED DESCRIPTION OF THE INVENTION

The invention has four stages or zones required for texturizing,stabilizing, shrinking and heat-setting, and finally winding or spoolingthe finished yarn product.

The invention is hereinafter described with reference to a number ofworking examples to illustrate the preferred embodiments as found in theproduction of an air-jet texturized polyester yarn.

Apparatus for the invention includes the sequential arrangement of fourdelivery means which may be in the form of paired rollers, godets orother suitable yarn conducting means followed by a winding means ortake-up spool, all being positively driven at controlled speeds asrepresented by circumferential speeds V₁, V₂, V₃, V₄ and V₅,respectively. A heater for the shrinking and heat-setting zone islocated between the third and fourth delivery means. The correspondingyarn tensions F_(n) can be designated as follows: F_(St) for thestabilizing zone between the second and third delivery means; and F₃, F₄and F₅ associated with the third and fourth delivery means and thetake-up spool, respectively. The initial multifilament yarn or thread issupplied from a feed bobbin through a tensioning means or guidepositioned just before the first roller or delivery means. Instead ofthis feed bobbin, the feed yarn can be directly supplied from aconventional melt-spinning unit and a yarn stretching means such asconventional feed and draw rolls wherein the first delivery means maytake the place of the draw rolls.

Following the first delivery means, the yarn passes through a liquidbath and then into an air-jet texturizer of conventional constructionsuch as that illustrated in the early Breen patents discussedhereinabove, it being understood that there are many variations andspecific improvements of such texturizers which may also be readilyadopted for purposes of the present invention.

In the texturizing zone between the second and third delivery means, theyarn is overfed to permit air-bulking in the texturizer withsubstantially no tension being exerted on the yarn as it runs out of thetexturizer into the stabilizing zone maintained over a heat-freeinterval between the second and third delivery means. It is essential tooperate third delivery means at a speed V₃ which is just sufficientlygreater than the run-in speed V₂ so as to pull out the so-calledmetastable loops without actually stretching or elastically orplastically deforming the individual yarn filaments. Because themetastable loops can be pulled out at a relatively low tension, e.g. atension F_(St) can be used which is below about 20 cN and preferablybelow about 15 cN, as shown in the following examples, using theInternational System of units where "cN" is the abbreviation forcentinewton or 10⁻² Newtons. On the other hand, the tension must besufficiently high in the stabilizing zone to produce a final yarnproduct with a boiling shrinkage below about 3.3% and an instability ofless than 1.0%, measured as defined above. For any given filamentaryyarn, this tension F_(St) must be maintained within narrow limits,preferably less than about 0.15 cN/dtex but higher than a minimum valueof about 0.025 cN/dtex. The required tension can be readily determinedby a few preliminary tests in order to preset the speeds V₂ and V₃, orelse conventional control means can be used to adjust the speed ratio V₃:V₂ in response to the tension measured by a tensiometer between thesecond and third delivery means. It is a special advantage of thepresent invention that this critical and essential tension in thestabilizing zone can be set and maintained independently of the optimumconditions in each of the other stages or zones of the overall process.

In Examples I to VII as set forth in the Table which follows, the yarnemployed was a polyethylene terephthalate yarn of 167 dtex f68. It canbe inferred from Examples I and IV of this Table that the run-out speedV₃ from the stabilizing zone is at least 2% greater than the run-inspeed V₂ in every case, and this drafting velocity is also limited inthat the winding speed V₅ should not exceed the speed V₂ at which theyarn leaves the texturizing zone. The optimum overdraft or pull outpercentage, as represented by the expression (V₃ -V₂)/(V₂)×100, isnecessarily dependent upon the composition and properties of theparticular yarn filaments and especially its pretreatment in thetexturizing zone. In general, an overdraft of about 2 to 8% isespecially preferred.

Example V shows that while an excessive overdraft in the stabilizingzone still provides good values of the amount of instability, thecrimping of looped texturizing previously introduced into the yarn isdamaged so badly that the yarn is no longer usable.

Example VI illustrates that one can achieve a good linear stability ofthe yarn without using any stabilizing zone by adopting the mostappropriate operating parameters in the setting zone and in the finalwinding or take-up zone. In this case, however, one must accept aconsiderable increase in the boiling shrinkage.

Example VII is another comparative example to show that the combinationof the stabilizing zone and the heating zone is required to achieve theunique and advantageous results of the present invention.

The overdraft to be applied in the stabilizing zone can be determined inadvance by applying a load to a standard one meter length of a sample ofthe texturized yarn, this load being selected so as to substantiallycompletely pull out the unstable or metastable loops but withoutstretching or plastically deforming the unheated yarn. It is thuspreferable to remove substantially all of the metastable loops. Forexample, a yarn texturized under the conditions of Example I, having alength of 1 meter under a base load of 0.01 g/denier, was subjected to alight load of 0.3 g/denier. The resulting change in length due to thislatter loading over the base load length of 1 meter, expressed as apercentage, is the upper and preferred limit of the overdraft of theyarn in the stabilizing zone of Examples II to V.

The following Table of Examples should be considered together with thenumerical designations given above to identify the various velocitiesand tension values

                                      TABLE                                       __________________________________________________________________________    Example                                                                            V.sub.1                                                                          V.sub.2                                                                          F.sub.St                                                                        V.sub.St                                                                         V.sub.3                                                                          F.sub.3                                                                         F.sub.4                                                                         V.sub.4                                                                          F.sub.5                                                                         V.sub.5                                                                          Inst.                                                                            KS                                          __________________________________________________________________________    I    625                                                                              500                                                                              --                                                                              0  -- 2 5 471                                                                              15                                                                              498                                                                              1.6                                                                              3.5                                         II   625                                                                              500                                                                               8                                                                              1  505                                                                              3 8 476                                                                              15                                                                              487                                                                              1.3                                                                              4.2                                         III  625                                                                              500                                                                              10                                                                              4  520                                                                              3 7 490                                                                              24                                                                              495                                                                              0.4                                                                              3                                           IV   625                                                                              500                                                                              14                                                                              6  530                                                                              3 7 499                                                                              17                                                                              502                                                                              0.7                                                                              3                                           V    625                                                                              500                                                                              30                                                                              10 553                                                                              4 7 493                                                                              Insufficient crimping,                                                        not usable.                                         VI   625                                                                              500                                                                              --                                                                              0  -- 8 79                                                                              508                                                                              20                                                                              503                                                                              1.0                                                                              4.2                                         VII  625                                                                              500                                                                              10                                                                              4  520                                                                              --                                                                              --                                                                               0  8                                                                              525                                                                              0.9                                                                              10                                          __________________________________________________________________________     V.sub.n represents yarn velocity (m/min)                                      F.sub.n represents yarn tension (cN)                                          F.sub.St represents yarn tension in the stabilizing zone (cN)                 V.sub.St represents overdraw in the stabilizing zone (%)                      Inst. represents Instability (%)                                              KS represents Boiling Shrinkage                                          

In addition to the tabulated Examples, tests were also run to show thatneither the stabilizing zone nor the setting zone, operated alone, willlead to the results achieved by the combination of both zones accordingto the invention. In one set of tests, samples were taken at differentpoints in the process as follows:

Sample 1--from the take-up spool;

Sample 2--between the third delivery means and the heater;

Sample 3--just behind, i.e. immediately following the second deliverymeans in the direction of yarn travel; and

Sample 4--just behind the fourth delivery means in the direction of yarntravel.

The height and width of the loops appearing in these samples were thenmeasured, as an average value in microns, with the following results:

    ______________________________________                                        Sample         Height  Width                                                  ______________________________________                                        1              32.7    21.3                                                   2              83.3    44.7                                                   3              78.7    42.7                                                   4              26.8    22.7                                                   ______________________________________                                    

Such results prove that only by using a combination of the stabilizingand heating zones does it become possible to reduce the loops to lessthan one-half with respect to both height and width. If the heating zoneis used without the stabilizing zone of the present invention, then theyarn was observed as being nonuniform and of poor quality, especiallybecause of an uneven distribution of loops and flat portions over thelength of the yarn.

It should be noted that the shrinkage and setting treatment of thirdstage has an essential purpose or function of modifying and improvingthe shrinkage properties so that the yarn is more useful in a largenumber of final textile products where shrinkage must be avoided.Package dyeing is also improved with such low shrinkage values. Theoptimum modifying treatment in the shrinking and setting zone dependsupon the type of yarn, i.e. the polymer used, denier, fiber propertiesand the desired characteristics of the final yarn. In general, it hasbeen found that the run-out speed from the shrinking and setting zone isnormally selected to be smaller than the run-in speed V₃. Good yarnproperties can be achieved, for example, if the run-out speed V₄ isapproximately 2 to 10% less than the run-in speed V₃. As shown in theExamples, yarns with a size of 167 dtex exhibited advantageouscharacteristics if the run-out speed of the setting zone was less thanthe run-in speed to the stabilizing zone.

In certain instances, especially for nylon and polyester yarns of morethan 700 dtex, the shrinkage properties of the texturized yarn arepreferably modified by a heat treatment with the run-out speed V₄ fromthe setting zone being about equal to or only up to 2% higher than therun-in speed to the same zone.

The principal advantage and improvement of the process and correspondingapparatus of the invention arises out of the discovery that the qualityand usefulness of the jet-texturized yarn improves significantly by theaddition of a separate stabilizing zone between the texturizing zone anda heat-setting zone. With respect to the apparatus, this modification ofthe process requires only the addition of an additional set of deliveryrolls or similar yarn conducting or delivery means and a generally knowntubular heating means to provide the essential shrinking and setting ofthe yarn following the stabilizing zone. As a result of this simple butsignificant change in the air-jet texturizing process, it becomespossible to carry out both the setting and winding operations underoptimum conditions of speed and tension.

The exact length of the stabilizing zone is not critical but it shouldbe sufficiently long to achieve a uniform pulling out of the metastableloops, i.e. so that the overdraft is uniformly integrated or equalizedover the yarn length without causing local elastic or plasticdeformation of filaments. The term "elastic deformation" refers to anelongation of a filament which may then substantially recover to itsoriginal length. The expression "plastic deformation" refers to astretching of the filament to the point where it is permanentlyelongated and has its fiber properties markedly changed if notcompletely damaged. Such deformations must be avoided in pulling out themetastable loops in the stabilizing zone of the present invention.

The preferred velocity or yarn speed relationships with reference toeach other at various points in the process are set forth by the claimsbelow and are incorporated here by reference. The preferred polyesteryarn (polyethylene terephthalate) is one with a yarn size on the orderof magnitude of about 167 to 267 dtex.

Especially valuable yarns are obtained according to the presentinvention by bringing together individual yarns from identicaltexturizing and stabilizing zones and combining them into a two-ply orthree-ply yarn with an identical shrinking and heat treatment of theindividual yarns. These plied yarns have the same improved stability andlow boiling shrinkage as the single ply yarns and provide a very highquality fabric or webbing as a final textile product.

With the yarns produced according to the present invention, linearstability is increased substantially, the boiling shrinkage and the burreffect are both greatly reduced and the overhead unwinding or run-offfrom a spool or bobbin package is improved to such an extent that itbecomes possible to produce direct windings after air-jet texturizinginto a spool package which are immediately useful for spinning, weavingor knitting operations with delivery times of several hours and free ofthread breakages. No irregularity has been detected in the crimping ortexturized looping of the yarns produced by the process of thisinvention, even though there is a much shorter running length from thefourth delivery system and the winding spool. It should be noted as aparticular advantage that the form of the yarn with respect to thefrequency and appearance of the loops is already determined along withthe physical or structural properties of the yarn prior to the heattreatment so that this loop configuration of the yarn is notsubstantially modified other than to pull out metastable loops. Thevariation in bulking or hiding power is of less importance where, ashere, the stability and shrinkage properties represent a substantialadvance in this art.

The invention is hereby claimed as follows:
 1. A process for theproduction of a linearly stable, crimped continuous multifilament yarnwhich comprises:guiding the initial non-crimped multifilament yarnbetween a first and second delivery system through an air-jettexturizing nozzle as a texturizing zone at .Iadd.a temperatureinsufficient to heat set the yarn and at .Iaddend.an overfeed ratecorresponding to a circumferential speed V₂ of the second deliverysystem which is less than the circumferential speed V₁ of the firstdelivery system, thereby forming multiple random loops in the individualfilaments including a minor proportion of metastable loops;.Iadd.eliminating or at least pulling out to a stable position apredominant number of said metastable loops without removing the otherrandom loops and without any elastic or plastic deformation of theindividual filaments by .Iaddend.conducting the yarn immediately afterit has left the texturizing zone into a heat-free stabilizing zone bymeans of a third delivery system having a run-out speed V₃ greater thanthe run-in speed V₂ of the second delivery system.[., such thatmetastable loops are pulled out of the yarn without causing any elasticor plastic deformation of the individual filaments.].; then conductingthe stabilized yarn into a setting zone by means of a fourth deliverysystem having a run-out circumferential speed V₄ which allows a.Iadd.controlled .Iaddend.shrinkage of the yarn to a predeterminedamount, the yarn in said setting zone being subjected to a shrinkingtreatment and heat treatment at temperatures from 150° C. up to about245° C.; and winding the yarn after said shrinkage onto a spool at apredetermined yarn tension and at a winding speed V₅ which is less thanV₁.
 2. A process as claimed in claim 1 wherein the run-out speed V₃ fromthe stabilizing zone is less than the run-in speed V₁ into thetexturizing zone.
 3. A process as claimed in claim 1 wherein the windingspeed V₅ is less than V₂.
 4. A process as claimed in claim 1 wherein therun-in speed V₁ into the texturizing zone is up to 300% greater than therun-out speed V₂ from said texturizing zone.
 5. A process as claimed inclaim 1 wherein the run-in speed V₁ into the texturizing zone is up to25% greater than the run-out speed V₂ from said texturizing zone.
 6. Aprocess as claimed in claim 1 wherein the run-out speed V₃ from thestabilizing zone is 2 to 30% greater than the run-in speed V₂ into saidstabilizing zone.
 7. A process as claimed in claim 1 wherein the run-outspeed V₃ from the stabilizing zone is 2 to 15% greater than the run-inspeed V₂ into said stabilizing zone.
 8. A process as claimed in claims1, 6 or 7 wherein the run-out speed V₄ of the setting zone is about 2 to10% less than the run-out speed V₃ of the stabilizing zone.
 9. A processas claimed in claim 1 wherein the run-out speed V₄ of the setting zoneis less than the run-in speed V₃ of said setting zone.
 10. A process asclaimed in claim 9 for producing a low shrinkage yarn having a lineardensity higher than 70 dtex wherein the run-out speed V₄ of the settingzone is less than the run-in speed V₂ of the stabilizing zone.
 11. Aprocess as claimed in claim 1 wherein the winding speed V₅ isapproximately equal to the run-out speed V₄ of the setting zone but lessthan the run-out speed V₃ of the stabilizing zone.
 12. A process asclaimed in claim 1 wherein the pulling out of the yarn in thestabilizing zone is less than the change in length of the same yarn ifit were to be subjected to the shrinking and heat treatment immediatelyafter the texturizing zone and then subjected to a weight load of 0.3g/den for 30 seconds duration.
 13. A process as claimed in claim 1wherein the yarn being used is a multifilament yarn of polyethyleneterephthalate.
 14. A process as claimed in claim 1 wherein the yarnbeing used is a multifilament yarn of polyethylene terephthalate whichhas been spun at a spinning speed of more than 2,500 m/min andsubsequently stretched in the ratio of 1:1.2 to 1:2 before beingintroduced into the texturizing zone.
 15. A process as claimed in claims13 of 14 wherein the yarn has a linear density on the order of 167 dtex.16. A process as claimed in claims 13 or 14 wherein the yarn has alinear density on the order of 267 dtex.
 17. A process as claimed inclaim 1 wherein a number of yarns from identical texturizing andstabilizing zones are combined into a two-ply or three-ply yarn with anidentical shrinking and heat treatment of the individual yarns.
 18. Theair-jet texturized and linearly stabilized yarn product obtained by theprocess of claim 1, said yarn product having a boiling shrinkage of lessthan 3.3% and an instability of less than 1.0%, measured as thepercentage increase in yarn length of a sample having an initial lengthof one meter under a base load of 1/100 g/den after being subjected to aload of 1/3 g/den for 30 seconds and then relieved again to the baseload of 1/100 g/den for another 30 seconds.
 19. The yarn product asclaimed in claim 18 wherein two or three identically texturized andstabilized yarns are combined into a corresponding three ply yarn withall of the individual yarns having been subjected to an identicalshrinking and heat treatment.
 20. The yarn product as claimed in claims18 or 19 wherein each individual yarn is a multifilament polyethyleneterephthalate yarn.
 21. The yarn product as claimed in claim 18 woundonto said spool after said shrinkage at a predetermined yarn tension andsufficiently stabilized to provide run-off properties permitting thespool to be introduced directly onto a knitting or weaving machinewithout respooling.
 22. The spooled yarn product of claim 21 wherein theyarn is a multifilament polyethylene terephthalate yarn.